Father gave 6-month old prunes without mother's consent is that OK?

My granddaughter's 18 yr old father gave her prunes and Karo syrup to battle what he said was constipation. My daughter, the mom, doesn't know if the baby was given enough formula during the course of the day to know if maybe the constipation was due to the lack of fluid. Without ever having prunes introduced to her diet do we need to worry? She did have a normal bowel movement the next day